Method and apparatus for finding the lengthwise center of a workpiece

ABSTRACT

Disclosed here are methods and automatic apparatus for grinding cylindrical workpieces, such as the contoured rolls used in metal rolling mills. The methods and apparatus involve (1) automatic finding of the lengthwise center of rolls of different and undetermined lengths so as to establish a reference position for the execution of a numerically programmed path defined relative to the center of a roll as a point of symmetry, (2) the storage of the successive instructions of multi-axis movements making up a numerically defined profile or contoured path, and the use of those instructions repeatedly and in whole or in part as called for by different ones of a sequence of commands read from storage and executed in succession, (3) the automatic alignment of the roll axis parallel to the longitudinal axis of motion in a grinding machine by pivoting of one end of the roll about the other until the sensed difference in positions of the roll surface, along an axis transverse to the longitudinal axis and at locations near opposite ends of the roll, is changed to a predetermined fraction of the originally sensed difference, (4) the initiation of grinding passes from that end of a roll which is largest in diameter, so as to avoid &#39;&#39;&#39;&#39;digging in&#39;&#39;&#39;&#39; or increasing the depth of wheel bite as the wheel moves lengthwise of the roll, (5) the execution of continuous passes of the grinding wheel with preprogrammed values of feed rate, wheel speed, roll speed, continuous infeed and incremental infeed until a preprogrammed thickness of material has been removed from the roll surface, and (6) the grinding down of a roll until it is reduced to a diameter equal that of a previously ground roll of a matched pair. These functions are all obtained by the calling out and execution of preestablished routines in response to the reading from storage of preprogrammed sequence commands, so that in the disclosed method and apparatus there is an automatic progression from each type of operation to the next, and with the following of numerically defined profile whenever it is required.

United States Patent Clark, Jr.

[54] METHOD AND APPARATUS FOR FINDING THE LENGTHWISE CENTER OF A WORKPIECE Stephen C. Clark, Jr., Phoenixville, Pa.

The lngersoll Milling Machine Company, Rockford, Ill.

[22] Filed: Jan. 25, 1971 211 Appl.No.: 109,526

[72] Inventor:

[73] Assignee:

Related US. Application Data [62] Division of Ser. No. 790,323, Jan. 10, 1969.

[52] U.S. Cl. ..51/165 TP, 51/49, 51/289 R [51] ..'..B24b 5/04 [58] Field of Search ..51/49,165 R, 165 TP, 165.71,

5l/l65.74, 165.75, 165.76, 165.77, 289 R, 326, 327;82/14B,14D,21B

Primary Examiner-Lester M. Swingle Arrorneywolfe, Hubbard, Leydig, Voit & Osann 57 ABSTRACT Disclosed here are methods and automatic apparatus for [151 3,660,948 51 May 9,1972

grinding cylindrical workpieces, such as the contoured rolls used in metal rolling mills. The methods and apparatus involve (l) automatic finding of the lengthwise center of rolls of different and undetermined lengths so as to establish a reference position for the execution of a numerically programmed path defined relative to the center of a roll as a point of symmetry, (2) the storage of the successive instructions of multi-axis movements making up a numerically defined profile or con toured path, and the use of those instructions repeatedly and in whole or in part as called for by different ones of a sequence of commands read from storage and executed in succession, (3) the automatic alignment of the roll axis parallel to the longitudinal axis of motion in a grinding machine by pivoting of one end of the roll about the other until the sensed difference in positions of the roll surface, along an axis transverse to the longitudinal axis and at locations near opposite ends of the roll, is changed to a predetermined fraction of the originally sensed difference, (4) the initiation of grinding passes from that end of a roll which is largest in diameter, so as to avoid digging in or increasing the depth of wheel bite as the wheel moves lengthwise of the roll, (5) the execution of continuous passes of the grinding wheel with preprogrammed values of feed rate, wheel speed, roll speed, continuous infeed and incremental infeed until a preprogrammed thickness of material has been removed from the roll surface and (6) the grinding down of a roll until it is reduced to a diameter equal that of a previously ground roll of a matched pair. These functions are all obtained by the calling out and execution of preestablished routines in response to the reading from storage of preprogrammed sequence commands, so that in the disclosed method and apparatus there is an automatic progression from each type of operation to the next, and with the following of numerically defined profile whenever it is required.

9 Claims, 27 Drawing Figures PATENTEDMAY 91972 3.660848 sum 01 0F 18 st r 11 c. czar/5F A, W ym QM PATENTED MY 9 I972 SHEET Stephen C. C/Qr-AQJ 5 MHZ yaw M Q. Q60x 948 PATENTEUM 9 I 72 SHEET 0 6 [1F 18 Umq MVIZADTQ K LW cl 2% 4 w o PATENTEDMAY 91912 3,660,948 sum 07 ur 18 4'; g g b (1) PREsET cm'ss KJL 1 H74 r29 re 6| @fingggggu g l 8 u BIDIRECTIONAL.

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3; 169 0 PRE5ET GATEs PRESET am ss \as I PRESET GATES OUT DQ3 5 33 up BIDIRECTIONAL PULSEQ M 7m COUNTER Mm EQ ZERO TO FIG (5F 9 1| 252 YZEADOUT cATEs ll PRESET GATES ton3 n 0 IN FIG.IO OUT DIRECTION @C: sENsER PULSER BIDIRECTlONAL COUNTEIL READOUT GATES MVEMTO m PATENTED MAY 9 I972 SHEET 12 [1f 18 METHOD AND APPARATUS FOR FINDING THE LENGTIIWISE CENTER OF A WORKPIECE CROSS-REFERENCE TO A RELATED APPLICATION This application is a division of my copending application Ser. No. 790,323,filcd Jan. 10, I969.

TABLE OF CONTENTS Abstract of the disclosure Cross-reference to a related application.. Background of the invention. Summary of the invention Brief description of the drawln s I )escriptlon of preferred embod ments A. An exemplary machine tool B. Control instrumentalities on the grinding machine.

1. Feedback pulse generators Steadyrest servomotor. Sensing switches 4. Probe assemblies 5. Proximity switches (J. The control system in general.. 1. Contouring apparatus 2. Sequence command system. 3. Data manipulation apparatus Methods and apparatus for grinding a roll 1. Setup procedure 2. Location of lengthwise center; M61 (a) Movement of the swivel base to the center of B axis travel (1)) Setting the a e (e) Movement of i' ii; the e'iiii'i "as a"screen;"instants positions 18 (d) M. ement of wheel to center of roll. l9 3. Automatic alignment of the roll axis 23 (a) Startup operations 23 (b) Movement to location of first gaging band 25 (e) Bringing the wheel into touching contact with the 26 re (d) Grinding right ageband to predetermined depth. 27 (0) Movement of w tool to location of left gage band 28 (l') Grinding of the left ga big band 29 (g) Itctraction of the when free of the roll 29 (h) Sensing the location of the loft gaging I rear side of the l( 30 4 Determining direction of II t grinding pa grinding (a) Right and larger. 37 ,(I)) Left end larger 37 (e) Status oi the system prior to lirst grinding pass 35 ((1) First grinding pass and continuous passing. 39 (i) Case l-Material removal incomplete... 40 (ii) Case ll-Material removal complete 41 5. Rough Grinding 41 6. Finish Grinding 43 7. Sensing and Signalin I the Roll Diameter 44 8. Cleaning Up the R01 Surface by Sparking Passes 43 9. Polishing Passes E. Grinding a Second Roll to the Same Diameter 52 F. An Alternative Embodiment". 56

BACKGROUND OF THE INVENTION .The present invention relates in general to methods and apparatus for the turning of workpieces, and while it will find advantageous use in the operation of various machine tools, the invention is adapted to be applied with special advantages in the operation of grinding machines for shaping or renewing the shape of rolls such as those employed in metal rolling mills.

In the operation of large installations for the rolling of steel or aluminum into thin sheets or strips for coiling, the high inter-roll pressures and roll speeds result in severe wear of the surfaces of the individual rolls. The wear is often non-uniform, and any roll surface irregularities result in magnified surface imperfections in the sheets or strips. It is common practice to change the rolls in a given mill stand frequently, as often as once pcr 8 hour shift. When each worn roll is removed from the mill, there is a need to have its surface refinished or reground to nearly perfect smoothness and with the desired cylindrical shape (which may be a convex or concave contour lengthwise of the roll to compensate for roll loading-pressure and produce a desired cross sectional shape in the rolled strip). To keep a large mill, and the investment which it represents, operating efficiently, it is desirable to regrind worn rolls not only quickly so that they may be returned to service, but also with precision.

The increasingly severe shortage of skilled machinists leads to the result that manual control of grinding machines offers little prospect of satisfying the current demand for rapid and precise grinding of rolls. in the present instance, control of the grinding machine is automated and the speed and precision with which rolls may be ground are facilitated through the use of pro-calculated, programmed data of two kinds, viz., profile data which define the contour of the finished roll surface, and sequence commands which call for the execution of different routines in succession, and with preselected operating parameters. More particularly, the profile of the roll is determined by a program of successive instructions defining successive multi-axis movements which make up a desired contour or profile, and which may be followed in the machining of a plurality of rolls which are to have the same finished profile.

Preferably but not necessarily used in conjunction with such a profile program is a program of sequential commands, prepared individually for each roll or a group of identical rolls so as to bring about the desired sequence of successive operations, including calling out and using all or a part of the profile program when that is required in the machining of the roll.

The profile program is prepared by using the lengthwise center of the roll as an assumed zero or reference point and, in most instances, the profile is symmetrical about the lengthwise center. In order to grind the roll to the desired profile as designated by the profile program, it is necessary to determine the actual physical location of the lengthwise center of the roll relative to the grinding machine and to coordinate such location with the profile program prior to actual grinding so that the program will be matched with respect to the roll as positioncd axially in the machine.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide a method and apparatus for finding the lengthwise center of a workpiece such as a roll, and to establish a zero reference for a numerical control contouring program at such center, quickly and preferably automatically after the workpiece has been placed in a machine tool. A related object is to provide a method and apparatus for finding the lengthwise center of the workpiece even though the exact length of the workpiece is not known or measuredand even though the axial displacement of the workpiece in a numerically controlled machine tool is not determined by a painstaking and time-consuming set up procedure.

In a more detailed sense, the invention resides in the finding of the lengthwise center of the workpiece by detecting and signaling the physical positions of the and edges of the workpiece in a novel manner as an incident to movement of the machine tool carriage along the length of the workpiece. And the signals thus produced are utilized subsequently to center the carriage relative to the workpiece preparatory to other machine operations, including those operations controlled by the contouring program.

The foregoing summary of the invention and the advantageous objectives achieved thereby will be better understood after consideration of the more detailed description of a specific, exemplary embodiment of the methods and apparatus. Additional advantages will also become apparent as the detailed description proceeds with-reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the attached drawings:

FIG. 1 is a fragmentary plan view, partly in diagrammatic form, of an exemplary grinding machine; I

FIG. 2 is a vertical section taken substantially along the offset line 22 of FIG. 1;

FIG. 3 is a diagrammatic illustration of the spacial relationship of two probe assemblies and a roll in the grinding machine;

FIG. 4 is a diagrammatic cross section showing the basic organization of'the two probe assemblies;

FIG. 5 is an end view, taken substantially along the line 5-5 of FIG. 4, of the rear probe assembly and showing the relationship of two proximity switches carried thereby; 

1. The method of machining a workpiece to have a surface contour which is symmetrical about a center point between first and second opposite edges spaced apart on the workpiece in the direction of one of a plurality of axes of relative motion between a tool and the workpiece, comprising the steps of bringing a workpiece sensor, which is relatively movable with the tool along said one axis, into operative position relative to the surface of the workpiece; initiating first relative motion of the tool in one direction along said one axis and terminating such motion in response to detection by said sensor of the first edge of the workpiece; initiating second relative motion of the tool in the opposite direction along said one axis and terminating such motion in response to detection by said sensor of the second edge of the workpiece; measuring and signaling the distance moved relatively by the tool in said opposite direction; initiating third relative motion of the tool in said one direction along said onE axis; utilizing said distance signaling to terminate the third motion when the movement thereof is equal to one-half the signaled distance; and thereafter numerically controlling plural axis relative motions of the tool according to a contouring program prepared with a zero reference point for said one axis midway between the two edges of the workpiece.
 2. The method of locating a reference point on a movable tool carrier at the midpoint of a workpiece having first and second edges spaced apart in the direction of a path along which the carrier is linearly movable relative to the workpiece, comprising the steps of bringing a workpiece sensor mounted at the reference point on the carrier into operative position adjacent the surface of the workpiece at any initial location along said path, initiating relative motion of the carrier along said path in one direction and terminating such motion in response to detection by said sensor of the first edge of the workpiece, initiating relative motion of the carrier along said path in the opposite direction and terminating such motion in response to detection by said sensor of the second edge of the workpiece, measuring and signaling by digital electrical signals the distance moved by the carrier in said opposite direction; initiating relative motion of the carrier along said path in said one direction, and utilizing said signals to terminate the latter motion in said one direction when it becomes equal to one-half the distance moved in said opposite direction, whereupon the sensor and the reference point on said carrier are located midway between the two edges of the workpiece.
 3. The method defined in claim 2, further including converting the digital signals representing distance moved in said opposite direction are into second digital signals representing 0ne-half of such distance, measuring the distance moved during the last motion in said one direction, and terminating such last motion when the measured distance becomes equal to the distance represented by said second digital signals.
 4. The method of locating a reference point on a movable tool carrier at the midpoint of a workpiece having first and second edges spaced apart in the direction of a path along which the carrier is linearly movable relative to the workpiece, comprising the steps of advancing a sensing head on the carrier in a direction substantially normal to the workpiece surface between said edges until two proximity switches on the head are operatively disposed relative to the surface at any initial location along said path, said proximity switches being usually spaced in a direction parallel to said path on opposite sides of said reference point, initiating first relative motion of said carrier in a first direction along said path and terminating such motion when a first one of said proximity switches ceases to sense the adjacent surface of the workpiece as a result of passing beyond the first edge, initiating second relative motion of said carrier in the opposite direction and signaling the instant at which said first proximity switch senses the adjacent surface of the workpiece at said first edge, continuing said second motion as a third motion of said carrier and terminating such motion when the second one of said proximity switches ceases to sense the adjacent surface of the workpiece as a result of passing beyond the second edge, utilizing the signaling from said first switch to initiate the measuring and digital signaling of the distance traveled by said carrier during said third motion, initiating a fourth motion of said carrier in said first direction and signaling the instant at which said second switch senses the adjacent surface of the workpiece at the second workpiece edge, measuring and subtractively combining the distance traveled by the carrier during said fourth motion with the digitally signaled distance traveled during said third motion to signal a net distance, continuing said fourth motion as a fifth motion in said first direction while mEasuring and signaling the distance traveled, and terminating said fifth motion when the latter signaling represents one-half of said signaled net distance.
 5. The method defined in claim 4 further characterized in that said first motion is executed at a traverse velocity, said second motion is executed at a creep velocity, said third motion is executed at a traverse velocity, said fourth motion is executed at a creep velocity, and said fifth motion is executed at a traverse velocity.
 6. The method defined in claim 4 further including converting the signals representing said net distance into second signals representing one-half of said net distance, counting increments of movement while said fifth motion is being executed, and terminating said fifth motion when the total of counted increments equals the distance represented by said second signals.
 7. In a machine tool adapted to receive a workpiece and having a member movable along a linear path generally parallel to the surface of the workpiece between two edges of the latter, the combination comprising a sensing head carried by said member and movable relative to the latter in a direction normal to said path, a proximity sensor carried by said sensing head and movable with the latter to reside adjacent the workpiece surface, means for registering and digitally signaling the distances moved by said member along said path, first control means for moving said head to locate the sensor in proximity to said workpiece surface, second control means for moving said member in one direction along the path until the workpiece surface at one edge is no longer sensed by said sensor, third control means for moving said member in the opposite direction along the path until the workpiece surface at the other edge is no longer sensed by the sensor, fourth control means for registering in said registering means the distance moved by the member under control of said third means, and fifth control means for moving said member in said one direction along the path through a distance equal to one-half of the distance previously registered and signaled in said registering means.
 8. The combination defined in claim 7 further characterized in that said means for registering and signaling comprises a pulse generator for producing a pulse for each increment moved along the path by said member and a counter responsive to said pulses, said fourth control means includes means for supplying pulses from said generator to said counter, and said fifth control means includes means for supplying pulses from said generator to said counter and means controlled by said counter for terminating the last movement in said one direction when the pulses so supplied represent one-half of the quantity registered in the counter under the control of said fourth means.
 9. The combination defined in claim 7 further characterized by means for producing an initiation signal to start said first control means, means responsive to completion of operation by said first control means for starting operation of said second control means, means responsive to completion of operation of said second control means for enabling said fourth control means and starting said third control means, and means responsive to completion of operation of said third control means for starting said fifth control means. 